President Biden ordered US military aircraft to strike targets on Syrian soil that the US claims were affiliated with two pro-Iranian militias, Kataib Hezbollah and Kataib Sayyid al-Shuhada. The US, working closely with Iraqi security services, has implicated Iranian-backed Shia militias in a recent rocket attack on a US airbase in Erbil, Iraq, that killed a foreign contractor employed by the US and wounded four American contractors and a US service member. 

A Pentagon spokesperson, John Kirby, called the attack, which was carried out by US F-15E aircraft and killed up to 17 people, a "proportionate military response" designed to send "an unambiguous message: President Biden will act to protect American and coalition personnel."